Prior art intraocular lenses, whether accommodative or single-focus, are typically implanted in the capsule of an eye from which the crystalline lens has been removed via a procedure that includes capsulorhexis. Because the capsulorhexis destroys the natural accommodation mechanism of the eye whereby the crystalline lens is elastically reconfigured to a diopter power appropriate for the visual task by the posterior forces exerted by the anterior capsule and the anterior forces exerted by the posterior capsule, the visual accommodation must be provided in some other way.
Because the crystalline lens is also both a spacer between the anterior and posterior capsules and a determinant of the zonule-proximal capsule curvature, and thus a determinant of the zonular load distribution in the natural eye, these crystalline lens functions, which are lost by its extraction, must also be addressed. Most of the accommodative intraocular lenses in the prior art assume the validity of the Helmholtz Theory of Accommodation—i.e., that tension on the zonules increases the equatorial diameter of the capsule and flattens the capsule, and thus flattens the crystalline lens therein to a shape appropriate for a distant vision, while contraction of the ciliary body muscle(s) reduces zonular tension and allows the elastically reconfigurable crystalline lens to assume a more convex (accommodative) shape. Thus, lens assemblies implanted in capsules and having accommodating mechanisms responsive to these changes in diameter should be able to provide the visual accommodation despite the capsulorhexis.
The prior art includes tens, if not hundreds, of examples of lenses intended to provide accommodation on this basis. Most of these lenses can be demonstrated to work as expected in vitro. None of the lenses, however, work as expected in vivo. For example, the named inventors of U.S. Patent Application Publication Nos. 2009/0234449 (De Juan, Jr., et al.) and 2007/0100445 (Shadduck), attribute this failure to “shrink-wrapping,” and disclose spacers intended to prevent this failure by maintaining a separation of the anterior and posterior capsules. While “shrink-wrapping” may be a contributing factor to this failure, its elimination has not solved the problem.
There are, however, two kinds of prior art intraocular lenses that can be implanted in capsulorhexis-crippled capsules that provide some degree of accommodation. One is a Fresnel configuration that is disclosed in U.S. Patent Application Publication No. 2007/0171362 (Simpson). ReStor™, ReZoom™ and Tecris™ are known trade names for such lenses. These lenses are not intended to respond to a change in capsular diameter, but instead have zones of different diopter power, some of which are appropriate for distance vision and others for reading. The well-known shortcomings of such lenses, however, include loss of contrast, halos, etc.
The other is an intraocular lens assembly that is disclosed in U.S. Pat. No. 6,849,091 to Cumming and other U.S. Patents and published U.S. Patent Applications by the same inventor (“Cumming”). Crystalens™ is a known trade name for such lens assemblies. These intraocular lens assemblies are anchored equatorially in capsulorhexis-crippled capsules by “shrink-wrapping,” and accommodation is provided by anterior movement of the lens in response to forces exerted anteriorly upon the portion of the lens assembly that is in contact with the posterior capsule. Cumming attributes these forces to “viscous pressure” from the vitreous humor. Thus the Crystalens™, which achieves some degree of visual accommodation, does so in direct opposition to Helmholtz, who teaches disaccommodation via flattening of the capsule—i.e., anterior translation of the posterior capsule. De Juan, Jr. also discloses the use of “viscous pressure” to provide the visual accommodation.[6]
U.S. Patent Application Publication No. 2007/0032867 to Cumming discloses translational accommodative intraocular lenses having plate-type haptics with “T” shaped ends, and U.S. Pat. No. 7,985,253 to the same inventor discloses hydraulic accommodative intraocular lenses in which the “T” shaped ends are curly. Plate-type haptics are familiar from commercially available intraocular lenses, and both the “T” shaped and the curly ends are variations of the “J” type haptics familiar from the prior art that, like the “J” type haptics, secure the lens to the capsule by the “shrink-wrapping” of the latter.
U.S. Pat. No. 2,300,251 to Flint discloses variable focus hydraulic lenses of the kind employed by Cumming's hydraulic lens systems, and U.S. Pat. No. 4,261,655 to Honigsbaum teaches eyeglasses having adjustable focus hydraulic lenses in which a part of the focusing mechanism is a bellows-like arrangement.
U.S. Patent Application Publication No. 2011/0035001 to Woods discloses spacer-like “optics positioning members” that are implanted into capsules and that are intended to provide the visual accommodation by appropriately positioning lens elements in response to zonular tension-induced changes in capsule shape, and are expected to do so despite the unaddressed crippling effects of capsulorhexis.
U.S. Patent Application Publication No. 2012/0253459 to Reich, et al. discloses a lens elastically reconfigured by means in direct contact with the ciliary structure of the eye.
U.S. Patent Application Publication No. 2007/0123981 to Tassignon (“Tassignon”) discloses the use of a ring as a guide or template for cutting an axisymmetric capsulorhexis as a part of a procedure for intraocular lens implantation, and a two part intraocular lens arrangement in which a “U” section haptic ring that embraces the margin of both an anterior and posterior capsulorhexis holds a lens that is separable from its haptic ring. Tassignon also states that such an arrangement can provide accommodation on the basis of changes in the capsular diameter.
U.S. Pat. No. 4,822,360 to Deacon, U.S. Pat. No. 7,156,101 to Terwee, and U.S. Patent Application Publication No. 2012/0226351 to Peyman disclose intracapsular lenses intended to replace the natural crystalline lens. Because the implantation of such lenses in a fully functional state would require an unacceptably large corneal incision, the patents disclose implantation of the lens as an uncured polymer that is to be cured and shaped in vivo. The patents do not, however, disclose how the lens-shaping function of the anterior capsule compromised by capsulorhexis during the removal of the natural lens is restored.
U.S. Patent Application Publication No. 2012/0303118 to DeBoer, et al. (“DeBoer”) discloses a bag-type crystalline lens replacement that is implanted uninflated via a small equator-proximal anterior capsule incision that is also used for lensectomy. The lens is then “inflated” with silicone oil to the desired size and shape. DeBoer also discloses a plurality of self-sealing post-implantation bag access ports. Such ports are familiar from known art, such as spray-can valves.
U.S. Patent Application Publication No. 2007/0213817 to Esch, et al. discloses hydraulic lens assemblies having tubular ring haptics in which a portion of the actuating fluid is contained.
Surgical glues are commercially available under trade names such as BioGlue™, TissueGlu™, etc., and U.S. Patent Application Publication No. 2011/0029074 to Reisin, et al. discloses alternatives to the commercially available surgical glue products.
U.S. Patent Application Publication No. 2013/0013061 to Coroneo (“Coroneo”) discloses a “U” section ring for permanent insertion into a capsulorhexis to apply centrifugal forces to capsulorhexis-crippled anterior or posterior capsules to address phimosis. Tassignon [13] discloses a similar section ring for centrifugal forces but for a different purpose. While Coroneo uses the term “capsular tension rings” (CTR), Coroneo's CTRs are the familiar “C” shaped rings inserted into some capsules to apply centrifugal forces to address phimosis. Such CTRs are available commercially from FCI Opthalmics and others, and, like the Coroneo ring, apply centrifugal forces to the capsule.
U.S. Patent Application Publication No. 2013/0304206 to Pallikaris, et al. (“Pallikaris”) discloses zonules that originate at the ciliary body muscle and insert both anteriorly and posteriorly at the equatorial region of the capsule, thus centrifugally tensioning the capsule. Pallikaris also discloses that, if the centripetal equatorial capsular tension lost by capsulorhexis and crystalline lens removal were restored, the decrease in zonular tension resulting from contraction of the ciliary body muscle would decrease the capsule diameter, and that this change in capsular diameter could actuate an accommodative intraocular lens.
Pallikaris further discloses three mechanisms to restore the centripetal tension: (1) a tensioning ring glued equatorially to the capsule interior, (2) a comb-like equatorial compression ring the tines of which are implanted between the zonules, and (3) an interior capsule equator tensioning ring held in place by clamps and/or grooves that secure a further surgically modified anterior capsule to the ring.
Capsules are of course soft tissue, and lens implants are expected to serve the patient for the rest of his/her life—i.e., for two decades or more, and there are no soft tissue glues that can serve their intended purpose for anywhere near this length of time.
There are about 72 zonules, roughly half anterior and half posterior, and implanting anywhere near this complement of compression ring tines between both anterior and posterior zonules without damage to the zonules and/or the tines is a virtually impossible task.
The three mechanisms for restoring centripetal tensions are based upon the assumption that the zonules originate at the ciliary body muscle and insert both anteriorly and posteriorly at the equatorial region of the capsule. Both in-vivo studies (e.g., “Extralenticular and Lenticular Aspects of Accommodation and Presbyopia in Human vs. Monkey Eyes,” IOVS Manuscript, IOVS 12-10846, Jun. 6, 2013 by M. A. Croft, et al. (“Croft”)) and in-vitro studies (e.g., “Evidence for Posterior Zonular Fiber Attachment on the Anterior Hyaloid Membrane,” IOVS Vol. 47, No. 11, November 2006 by Bernal, et al. (“Bernal”)) confirm, however, that at least some of the zonules originate elsewhere on the ciliary body, and also confirm that at least some of the posterior zonules insert at the hyaloid membrane before inserting at the posterior capsule. Thus, the change in zonular tension moves the capsule equator anteriorly and posteriorly with respect to the tensioning device or rotates the tensioning devise about the axis of its cross-section, or both.
This applies peel-type loading to the glued version (which is the kind of loading to which glue bonds are most vulnerable), a saw-type motion to the tines of the comb-like version (which can cut the zonules and/or the tines), and accommodation when disaccommodation is expected (and vice versa) when a surgically modified anterior capsule is attached to a capsule-equator-based tensioning ring.
The Croft and Bernal studies are of particular interest because they both offer evidence that at least some, if not all, of the posterior zonules insert at the anterior hyaloid membrane before inserting at the posterior capsule. Thus, the anterior translation of the posterior capsule is constrained while the anterior capsule is free to translate posteriorly in response to anterior zonule tension because the anterior zonules insert directly at the anterior capsule. This not only explains the visual accommodation mechanism of the human eye, which is a combination of translation and elastic reconfiguration, but it also explains the need to restore the centripetal anterior capsule forces lost by capsulorhexis if the accommodative intraocular lenses of this invention and/or those of the prior art are to serve their intended function.